I've never made rolled fondant (the recipe seemed too involved and like candy making --something I'm not good at). I very much dislike Wilton rolled fondant--to me it tastes like what modeling clay smells like (make sense?). I use the Pettinice brand rolled fondant which I find to be a superior product. But keep in mind: rolled fondant is originally a European product with a European taste. It bears no resemblance to out buttercreams, etc.
As for marshmallow fondant, I tried making it with no luck. No matter how much I worked it with additional confectioners' sugar and shortening (as suggested on various posts), I could not get it to be smooth and non-sticky like Pettincice rolled fondant. Just my opinion, mind you.